If you have a silver cased one, its not very hard at all. However the black anodized ones for Dell have an additional small lip on the front lower section that makes removing the cover a _serious_ PainInTheA$$.

I used a tiny screwdriver to gently push outwards on the
front lower fascia to make it possible to "pop" the runner
out. Be careful!!

Ed
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When I shoot MY super-computer, the bullets really DO bounce off. What about yours?